<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>404</title>
    <link rel=stylesheet type=text/css href="{{ url_for('static', filename='bootstrap.v4/css/bootstrap.min.css') }}">
<script src="{{url_for('static', filename='bootstrap.v4/js/jquery.min.js')}}"></script>
<script src="{{url_for('static', filename='bootstrap.v4/js/popper.min.js')}}"></script>
<script src="{{url_for('static', filename='bootstrap.v4/js/bootstrap.min.js')}}"></script>
</head>
<body>
    <div class="alert alert-success">This is 400 page</div>
</body>
</html>